He convinces his sister's nerd to have sex with her

A geeky sister is like a joker: you always know you have an easily accessible vagina where you can put your dick in almost the right way. So if the thing twists with your girlfriend or you're tired of the straws, maybe a good option is to make this guy and see if you convince your sister to put his dick in his mouth, suck it up and play good dust to enjoy that tight cunt which is usual for these inexperienced whores. The whore ends up thanking her brother for penetrating her.